Control method of generator

ABSTRACT

When drive control of a generator is performed, PWM control of a switching circuit comprising an FET and a diode connected to the opposite ends of a winding is performed. In the vicinity of a moment in time Lmax where the winding has a maximum inductance L, an alternating mode for repeating a supply mode and a reflux mode alternately is performed through PWM control. After the alternating mode is performed, the reflux mode is performed temporarily in order to increase the quantity of current, and then a regenerative mode is performed. The regenerative mode is performed by increasing the current level as much as possible when the reflux mode is started while suppressing the brake force of the rotor in the alternating mode. From a position advancing in angle by a time Tah from the moment in time Lmax where the winding has a maximum inductance L, a first alternating mode C 1  for repeating the supply mode P and the reflux mode Q alternately is performed. After the first alternating mode C 1  is performed, a second alternating mode C 2  for repeating the reflux mode Q and the regenerative mode R alternately is performed.

TECHNICAL FIELD

The present invention relates to a controlling method of a generatorwhich has an SR motor (Switched Reluctance Motor) structure.

BACKGROUND ART

Recently, in an electric automobile or a so-called hybrid car in which amotor and an engine are commonly used, it has been discussed not to usean expensive permanent magnet, but to use an SR motor that has a simpleand rigid structure, and excels in a high speed rotation and anenvironmental resistance. Generally, the SR motor has a construction inwhich a rotor made of magnetic steel sheet is disposed rotatablycoaxially with a stator inside the stator in which a coil is woundaround. Salient poles projecting inward are formed on an innerperipheral side of the stator, and a coil is wound around on thissalient pole to form a winding. Salient poles projecting outward areformed radially on an outer periphery of the rotor, and adapted toapproach, oppose and separate from the salient poles of the stator inassociation with the rotation of the rotor. The salient poles of therotor and the salient poles of the stator are set to even numbers sothat both the salient poles of the rotor and the salient poles of statordo not have a multiple relation with each other with the result thatwhen certain salient poles of the stator and the rotor are opposed, theother salient poles of the stator and the rotor are deviated at thepositions. That is, when the number of salient poles of the rotor is,for example, four, the number of salient poles of the stator is set tosix, and when the number of salient poles of the rotor is six, thenumber of salient poles of the stator is set to eight.

In such an SR motor, when current flows, for example, to a pair of theopposed windings of the stator, a magnetic flux directed from thesalient pole of the stator toward the salient pole of the rotor isgenerated. Thus, the salient pole of the rotor is attracted to thesalient pole of the stator to generate a torque at the rotor. Asdescribed above, the salient poles of the stator and the rotor are setso that when certain salient poles are opposed, a deviation arises atthe other salient poles. Therefore, the winding of the salient pole setto the state that the other salient poles are deviated, is applied withpower, the salient poles of the deviated state are attracted, and thusthe rotor is rotated. When this operation is continuously conducted, thesalient poles of the rotor are attracted to the salient poles of thestator continuously, and the rotor is rotated around its axis.

On the other hand, such an SR motor can be used as a generator, forexample, Japanese Patent Application Laid-Open Publication No.2001-57795 and Japanese Patent Application Laid-Open Publication No.2001-78490, disclose a control system for preventing overcurrent at apower generation time and thereby generating electricity in a highefficiency. In the Publication No. 2001-57795, a maximum amount ofcurrent, when a power regeneration is conducted at present time, ispredicted and calculated based on a rotational speed of the rotor or onan amount of supply current during a supply mode for using the SR motoras a motor by supplying a power from a battery. When the maximum amountof current reaches a predetermined rate, a regenerative mode in which anelectromotive force generated in the winding is recovered in the batteryis performed.

In the Publication No. 2001-78490, in addition to the above-mentionedsupply mode and regenerative mode, a reflux mode in which both ends ofthe winding are set to the same potential, is set. At the reflux modetime, the winding is short circuited, and hence winding currentincreases. A winding current value is always monitored. After the supplymode is switched to the regenerative mode, and when the winding currentvalue reaches a lower limit value, the regenerative mode is switched tothe above-mentioned reflux mode. In the reflux mode, a current valuerises, and when the current value reaches an upper limit value, thereflux mode is again switched to the regenerative mode. This switchingof the regenerative mode and the reflux mode is continued until therotor becomes a predetermined rotary angle. Thus, the winding currentvalue is controlled between the upper limit value and the lower limitvalue so as to prevent the winding current from becoming large in aprojecting manner.

Meanwhile, in the above-mentioned control system, in an inductancereducing region (dL/dθ<0), the current is controlled to fall within apredetermined range by means of the alternating mode and the refluxmode, and thereafter regenerative current flows. Since the currentflowing in the range of dL/dθ<0 affects a braking force to the rotor, itis necessary to suppress a control current value in thealternating/reflux mode to raise a power generating efficiency. However,when this control current value is suppressed to a small value, theregenerative current value is also reduced, and hence there is a problemthat it becomes difficult to assure a necessary amount of powergeneration. In order to control a motor current, a sensor for detectingthe current value and a feedback control circuit which is operated at ahigh speed are necessary. Hence, there is a problem that the apparatusbecomes expensive. An object of the present invention is to improve apower generating efficiency of a generator having an SR motor structure.

SUMMARY OF THE INVENTION

A controlling method of a generator according to the present inventionhaving a stator that has a plurality of salient poles, a rotor that hasa plurality of salient poles of a number (quantity) different from thesalient poles of the stator, and a winding wound around the stator,comprises: executing a reflux mode at both ends of the winding set tothe same potential after executing a supply mode for supplying a powerfrom a power source to the winding; and, after the reflux mode,executing a regenerative mode for recovering an electromotive forcegenerated in the winding to the power source.

In the present invention, after the supply mode is conducted, the refluxmode is executed, and thereafter the regenerative mode is carried out.In this manner, the regenerative mode is executed after the reflux modeis performed, the amount of current is raised once by the reflux modeafter a supply mode is conducted, the regenerative mode is then carriedout, and an amount of the regenerative energy in the regenerative modecan be increased, and hence the power generating efficiency is improved.

Further, another controlling method of a generator according to thepresent invention having a stator that has a plurality of salient poles,a rotor that has a plurality of salient poles of a number different fromthe salient poles of the stator, and a winding wound around the stator,comprises: executing an alternating mode for alternately repeating asupply mode for supplying a power from a power source to the winding anda reflux mode for setting both ends of the winding to the samepotential; and, after the alternating mode, further executing the refluxmode, thereafter executing a regenerative mode for recovering theelectromotive force generated in the winding to the power source.

In the present invention, an average current value in a region where thebrake force by the winding current is generated is being suppressed bythe alternating mode, and the regenerative mode is executed after thereflux mode is performed to raise the current value. Here, a risingtrend of the amount of current in the reflux mode is determinedaccording to the current value and the rotational speed of the rotor atthe reflux mode starting time. If they are not sufficiently large, theamount of current does not increase at the reflux mode time. When theincrease in the current at the reflux mode time is not sufficient, theamount of the regenerative energy in the regenerative mode cannot besecured, and the power generating efficiency decreases. Meanwhile, whenthe winding current is controlled to increase the amount of current atthe reflux mode starting time, the brake force increases accordingly.

In the controlling method of the present invention, the alternating modefor alternatively repeating the supply mode and the reflux mode isexecuted, and after this alternating mode, the reflux mode is furtherperformed, and thereafter the regenerative mode is carried out.Therefore, the amount of current can be increased at the reflux modestarting time while suppressing the brake force in the alternating mode,the brake force and the amount of the regenerative energy are controlledin a well-balanced manner, and the power generating efficiency can beimproved.

In the controlling method of the generator, the generator is controlledby a switching circuit having a switching element and a diode connectedto both ends of the winding, and the switching element is PWMcontrolled, to thereby execute the alternating mode.

In the controlling method of the generator, the voltage of the powersource is detected, and a continuation time of one or both of the supplymode and the reflux mode or one or both of the alternating mode and thereflux mode may be controlled based on the voltage value. Thus, theovercharging of the power source in the regenerative mode can beprevented.

Furthermore, another controlling method of a generator according to thepresent invention having a stator that has a plurality of salient poles,a rotor that has a plurality of salient poles of a number different fromthe salient poles of the stator, and a winding wound around the stator,comprises: executing a first alternating mode for alternately repeatinga supply mode for supplying a power from a power source to the windingand a reflux mode for setting both ends of the winding to the samepotential; and after the first alternating mode, executing a secondalternating mode for alternately repeating the reflux mode and theregenerative mode for recovering the electromotive force generated inthe winding to the power source.

In the present invention, since the second alternating mode is providedafter the first alternating mode and the reflux mode and theregenerative mode are repeated in this second alternating mode, a riseof the current in the reflux mode can be suitably suppressed in theregenerative mode. Therefore, the regenerative current rate can besecured to the maximum while suitably suppressing the maximum currentrate, and power generation in a well-balance manner between them can beperformed. Accordingly, a load on a power device is reduced, an elementhaving a large capacity is not required, and its cost can be reduced.Further, a winding current rate can be suppressed without adding acurrent sensor, a high-speed comparator or the like, and an increase incost due to the increase in the number of components can be prevented.

In the controlling method of the generator, the generator is controlledby a switching circuit having a switching element and a diode connectedto both ends of the winding, and the switching element is PWM controlledto thereby execute the first and second alternating modes.

In the controlling method of the generator, the first alternating modemay be started before the time point at which the inductance of thewinding becomes maximum. The first alternating mode is advanced from atime point at which an inductance becomes maximum in this manner, thecontinuation time of the first alternating mode is lengthened.Therefore, since the current rate at the second alternating modestarting time increases and a power generation rate can be increased,the present method is particularly effective in the case where the powergeneration rate is insufficient. Meanwhile, since the increase in thecurrent rate in the second alternating mode is suppressed, even when thewinding current rate is excessively increased due to a lead angle, thecurrent rate can be suitably suppressed. Therefore, according to thepresent invention, the increase in the current rate due to the leadangle and the suppression of the current rate in the second alternatingmode are combined in a well-balanced manner, so that it is possible torealize a preferable control state capable of sufficiently maintaining aregenerative current rate while suppressing the maximum current value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing a construction of a generatorapplied with a controlling method of an embodiment 1 of the presentinvention;

FIG. 2 is a circuit diagram showing a construction of a drive circuit inthe generator of FIG. 1;

FIG. 3 is a circuit diagram showing only a U-phase portion extractedfrom the circuit diagram of FIG. 2; wherein (a) shows a supply mode, (b)shows a regenerative mode, and (c) shows a reflux mode in thecontrolling method of the embodiment 1;

FIG. 4 is an explanatory view showing execution timing of each mode inany one of U-phase, V-phase and W-phase; wherein (a) shows therelationship between a rotary angle of a rotor and an inductance L, (b)shows the relationship between the rotary angle of the rotor and thewinding applying voltage, and (c) shows the relationship between therotary angle of the rotor and the winding current;

FIG. 5 is an explanatory view showing execution timing of each mode inthe controlling method of the embodiment 1; wherein (a) shows therelationship between the rotary angle of the rotor and the inductance L,(b) shows the energizing state of HI side and LO side in the drivecircuit, (c) shows the relationship between the rotary angle of therotor and the winding voltage, and (d) shows the relationship betweenthe rotary angle of the rotor and the winding current;

FIG. 6 is a circuit diagram showing only the U-phase portion extractedfrom the circuit diagram of FIG. 2; wherein (a) shows the supply mode,(b) shows the regenerative mode and (c) and (d) show reflux mode in thecontrolling method of an embodiment 2;

FIG. 7 is an explanatory view showing execution timing of each mode inthe controlling method of the embodiment 2 of the present invention;wherein (a) shows the relationship between the rotary angle of the rotorand the inductance L, (b) shows the energizing state of the HI side andthe LO side in the drive circuit, (c) shows the relationship between therotary angle of the rotor and the winding voltage, and (d) shows therelationship between the rotary angle of the rotor and the windingcurrent; and

FIG. 8 is an explanatory view showing execution timing of each mode inthe controlling method of an embodiment 3 of the present invention;wherein (a) shows the relationship between the rotary angle of the rotorand the inductance L, (b) shows the energizing state of the HI side andthe LO side in the drive circuit, (c) shows the relationship between therotary angle of the rotor and the winding voltage, and (d) shows therelationship between the rotary angle of the rotor and the windingcurrent.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

Now, the embodiments of the present invention will be described indetail with reference to the accompanying drawings. FIG. 1 is anexplanatory view showing a construction of a generator applied with acontrolling method of an embodiment 1 of the present invention. Agenerator 1 of FIG. 1 has a structure similar to a so-called SR motor,and comprises a stator 2, and a rotor 3 that is rotatably arrangedinside the stator 2. The stator 2 is contained in a housing (not shown).The generator 1 is driven, for example, by an automobile engine. In thiscase, the rotor 3 is coupled to a crankshaft of the engine. Thegenerator 1 of this embodiment is an inner rotor type, but may be anouter rotor type in which the positional relationship between the statorand the rotor is opposite.

The stator 2 has a stator core 4 and a plurality of windings 5. Thestator core 4 is formed by laminating a plurality of magnetic steelsheets, and fixed in the housing. The stator core 4 has a cylindricalyoke 6 and six salient poles 7 at the inside of the yoke 6. The salientpoles 7 inwardly project toward the radial direction of the yoke 6. Thewinding 5 is formed by winding a coil on each salient pole 7. Thegenerator 1 is a three-phase generator, and the winding 5 has U-phase,V-phase and W-phase windings 5Ua, 5Ub, 5Va, 5Vb, 5Wa, and 5Wb. A pair ofopposed windings 5 are connected in series to construct the respectivephase winding sets 5U, 5V and 5W.

The rotor 3 has a shaft 8 and a rotor core 9. The shaft 8 is rotatablysupported by bearings provided in the housing. The rotary angle of theshaft 8 is detected by a shaft position sensor 17 (refer to FIG. 2). Arotational speed of the rotor 3 can be calculated from a period and apulse width of the shaft position sensor 17. Incidentally, if arotational speed detecting sensor is separately provided, it may beutilized. The rotor core 9 is formed by laminating a plurality ofmagnetic steel sheets, and fixed to the shaft 8. Four salient poles 10are provided on an outer peripheral side of the rotor core 9. The rotor3 is coaxially inserted and placed in the stator 2, and a predeterminedgap is formed between the salient pole 10 and the salient pole 7 of thestator 2.

Such a generator 1 can be used as an SR motor by sequentially supplyingcurrent to windings 5 of the respective phases. Here, when the currentflows to the winding 5, a magnetic flux is generated directed from thesalient pole 7 of the stator 2 to the salient pole 10 of the rotor 3.For example, when the windings 5Va, 5Vb are applied with power in astate shown in FIG. 1, the salient poles 10 b of the rotor 3 locatednear the windings are attracted, a torque is generated, and hence therotor 3 moves in a counterclockwise direction. When the salient pole 7Vof the stator 2 is opposed to the salient pole 10 b of the rotor 3, apositional displacement arises between the salient poles 7W and 10 asince the stator 2 has six poles and the rotor 3 has four poles.

When the windings 5Wa, 5Wb of the salient pole 7W are applied withpower, then the salient pole 10 a is attracted to the salient pole 7W.At this time, a positional displacement arises between the salient poles7U and 10 b. Next, when the windings 5Ua, 5Ub of the salient pole 7U areapplied with power, the salient pole 10 b is attracted to the salientpole 7U. That is, when the windings 5 of the respective phases aresequentially applied with power, the salient poles 10 of the rotor 3 arecontinuously attracted to the salient poles 7 of the stator 2, the rotor3 rotates with the shaft 8 in the stator 2, and operates as the SRmotor.

FIG. 2 is a circuit diagram showing a construction of a drive circuit inthe generator of FIG. 1. As shown in FIG. 2, switching circuit 19 havingFETs (switching elements) and diodes is connected to both ends of thewinding sets 5U, 5V and 5W of the respective phases. The first end sides(HI side: UH, VH and WH) of the winding sets 5U, 5V and 5W are connectedto a positive (+) electrode of a battery (power source) 16 through theFETs 11U, 11V and 11W, respectively and also connected (grounded) to anegative (−) electrode of the battery 16 through the diodes 13U, 13V and13W, respectively. The other (second) end sides (LO side: UL, VL and WL)of the winding sets 5U, 5V and 5W are connected to the positiveelectrode of the battery 16 through the diodes 14U, 14V and 14W, andalso connected to the negative electrode of the battery 16 through theFETs 12U, 12V and 12W, respectively.

The FETs 11 and 12 are controlled by gate drivers 15U, 15V and 15W. Thegate drivers 15U, 15V and 15W are connected to a CPU 18, and controlledby the CPU 18. The generator 1 further has a shaft position sensor 17which can detect the rotary angle of the shaft 8. The output of theshaft position sensor 17 is inputted to the CPU 18. The CPU 18 controlsthe gate drivers 15U, 15V and 15W based on the detection signal, andsuitably applies power to the winding sets 5U, 5V and 5W. The CPU 18calculates the rotational speed of the shaft 8 from the signal of theshaft position sensor 17. Incidentally, a voltage of the battery 16 ismonitored by the CPU 18 at all times.

FIG. 3 is a circuit diagram showing only the U-phase portion extractedfrom the circuit diagram of FIG. 2, FIG. 3( a) shows the supply mode,FIG. 3( b) shows the regenerative mode, and FIG. 3( c) shows the refluxmode. Incidentally, the following description will be made only for theU-phase, and the V-phase and the W-phase are operated similarly to theU-phase. In the controlling method, the generator 1 is driven by threecontrol modes of the supply mode, the regenerative mode and the refluxmode. The supply mode supplies power to the winding set 5U, theregenerative mode recovers an electromotive force generated in thewinding set 5U, and the reflux mode short circuits both ends of thewinding set 5U as the same potential.

In the supply mode, as shown in FIG. 3( a), the FETs 11U and 12U areturned ON simultaneously. In this mode, a current flows in a routethrough the FET 11U, the winding set 5U and the FET 12U. Thus, thebattery 16 supplies power to the windings 5Ua, 5Ub of the winding set5U, the salient poles 10 of the rotor 3 are attracted to the salientpoles 7U of the stator 2, and hence the rotor 3 is rotated or braked.

In the regenerative mode, as shown in FIG. 3( b), the FETs 11U, 12U areturned OFF simultaneously. When the FETs 11U, 12U are turned OFF, apower supply from the battery 16 to the winding set 5U is stopped. Atthis time, an electromotive force for holding the magnetic flux isgenerated in the winding set 5U. In this mode, a current flows in aroute through the diode 13U, the winding set 5U and the diode 14U bythis electromotive force. Thus, an energy is regenerated in the battery16.

In the reflux mode, as shown in FIG. 3( c), the FET 11U is turned OFF,and the FET 12U is turned ON. Even in this state, the power supply fromthe battery 16 to the windings 5Ua, 5Ub is stopped, and an electromotiveforce is generated in the windings 5Ua, 5Ub. In this mode, a currentflows in a route through the diode 13U, the winding set 5U, the FET 12Uby this electromotive force. That is, both ends of the winding set 5Uare grounded, and the current refluxes through the aforementioned routeduring the reflux mode. Incidentally, the FET 11U may be turned ON, andthe FET 12U may be turned OFF to perform the reflux mode.

In the controlling method of the generator according to the presentinvention, the above-mentioned three types of the modes are performed asdescribed below. FIG. 4 is an explanatory view showing execution timingof each mode in any one of U-phase, V-phase and W-phase, any of theabscissa axes show a rotary angle of the rotor 3. FIG. 4( a) shows therelationship between the rotary angle of the rotor and the inductance L,FIG. 4( b) shows the relationship between the rotary angle of the rotorand the winding applying voltage, and FIG. 4( c) shows the relationshipbetween the rotary angle of the rotor and the winding current.

As shown in FIG. 4, in this embodiment, when the inductance L becomesthe maximum value Lmax (change rate (dL/dθ) of the inductance L is “0”),the power supply to the winding 5 is started. The power supply to thewinding 5 is PWM controlled by the gate drivers 15U, 15V and 15W. Thatis, the supply current rate to the winding 5 is controlled by thecontinuation time and the duty ratio under the ON/OFF control of the FET11U or the like, and the alternating mode for alternatively repeatingthe supply mode and the reflux mode is executed. The continuation timeTd of the alternating mode is set in response to the rotational speed ofthe rotor calculated from the signal of the shaft position sensor 17. Atthis time, Td can be set by the rotary angle of the rotor, and may beset to a predetermined angle irrespective of the rotational speed or toan angle in response to the rotational speed.

At the supply mode execution time (portion P in FIG. 4( c)) during thealternating mode, the winding current increases, while at the refluxmode execution time (portion Q in FIG. 4( c)), the winding currentdecreases. Here, the reduction part of the winding current in the refluxmode is smaller than the increase part of the winding current in thesupply mode, and during the alternating mode, the PWM duty ratio is setso that the current waveform to generally increases in the sawtooth-likewaveform.

After the time Td is elapsed, the CPU 18 stops the PWM control, and onlythe reflux mode is performed. Thus, the current flowing to the winding 5increases. After the reflux mode is performed for a predetermined period(or a predetermined rotary angle of the rotor), the regenerative mode isexecuted. When the regenerative mode is performed, the winding voltagebecomes −E, and the winding current i is gradually decreased to become“0” shortly. Thus, an energy of an amount shown by an area of a portionR of FIG. 4( c) is regenerated to the battery 16. Since the amount ofthe regenerative energy is determined depending upon the current rate atthe regenerative mode starting time, the amount of regenerative energychanges according to the duty ratio of the PWM control, a power sourcevoltage, continuation time Td of the alternating mode, reflux modeexecution time after the alternating mode, etc. The CPU 18 controls theamount of the regenerative energy by suitably regulating these values.

Further, the CPU 18 always monitors the voltage of the battery 16, andconducts a PI control by a voltage feedback, thereby preventing thebattery 16 from being overcharged. In this case, the PWM duty ratio andthe continuation time in the alternating mode may be suitably controlledwhile observing the battery voltage so as to set the battery voltage ata predetermined value. Note that, in the PWM control, stability of thevoltage value is important to ensure the control accuracy, and thedetection of the battery voltage is also important in this point.

As shown in FIG. 4( c), in the controlling method, since the reflux modeis once executed after the alternating mode, the reflux mode is switchedto the regenerative mode in the state in which the winding current rateis increased. Therefore, an amount of the regenerative energy (a area ofa portion R) at the regenerative mode execution time (portion R in FIG.4( c)) can be made large, and a power generating efficiency can beraised. Here, a rising trend of the current rate in the reflux mode isdetermined depending on the current value and the rotational speed ofthe rotor at the reflux mode starting time. If they are not sufficientlylarge, the current value does not increase at the reflux mode time. Whenthe current increase at the reflux mode time is not sufficient, theamount of the regenerative energy in the regenerative mode can not beensured, therefore the power generating efficiency is lowered. On thecontrary, when the winding current is controlled so as to increase thecurrent value at the reflux mode starting time, as a result of this, thebrake force increases. In the controlling method of the presentembodiment, an average current value in a region for generating a brakeforce by the winding current is suppressed by the alternating mode, andthe current value at the reflux mode starting time can be controlled tobecome as large as possible while suppressing such a brake force.Therefore, the brake force and the amount of the regenerative energy canbe controlled in a well-balanced manner, and the power generatingefficiency is improved.

Incidentally, since the SR motor is executed by the PWM control in anormal motoring operation in many cases, the power generation operationcan be performed in the above-mentioned control state withoutintroducing a new circuit or control mode. Therefore, the existingapparatus can deal with the controlling method of the present invention,and power generating efficiency can be improved without increasing thecost.

Embodiment 2

In the meantime, in order to increase the power generation rate in acontrol method as in the embodiment 1, it is necessary to increase awinding current value in the alternating mode. To this end, there arisesa need to raise the ON duty ratio under the PWM control in analternating mode time or to lengthen the energizing time. However, whenthe winding current value in the alternating mode time is increased,there is a problem that the current value in the reflux mode executedafter the alternating mode excessively increases. That is, as shown inFIG. 5, the maximum value imax of the winding current value i becomeslarge. If the winding current value i excessively increases, a load onthe power device is increased, and hence elements of large capacity mustbe used, which thereby increases the cost.

In this case, as in the above-mentioned Japanese Patent ApplicationLaid-Open Publication No. 2001-78490, when the reflux mode and theregenerative mode are switched while monitoring the current value, theexcess current can be suppressed, and the load on the power device canbe alleviated. However, to monitor the current value, a sensor fordetecting the current value and a feedback control circuit operating ata high speed are necessary. That is, when a current monitor system isadopted, the load on the power device can be alleviated but since thesensor, the high-speed comparator, etc., are newly used, the problem ofcost increase is still not solved. Therefore, the present inventor hasconsidered the structure of the embodiment to prevent the excessivecurrent generation in the generator of the SR motor structure withoutincreasing the cost.

FIG. 6 is a circuit diagram showing only the U-phase portion extractedfrom the circuit diagram of FIG. 2; and FIG. 6( a) shows the supplymode, FIG. 6( b) shows the regenerative mode, and FIGS. 6( c) and 6(d)show the reflux mode in the controlling method of the embodiment 2 ofthe present invention. Incidentally, in the following embodiment, thestructures of the generator and its drive circuit are similar to thoseshown in FIGS. 1 and 2, and the similar members and parts, etc. aredesignated by the same reference numbers, and therefore the descriptionwill be omitted.

In the controlling method of this embodiment, the generator 1 is drivenin three control modes including the supply mode, the regenerative modeand the reflux mode. Here, different from the embodiment 1, there aretwo variations of the reflux mode as shown in FIGS. 6( c) and 6(d).First, in the case of FIG. 6( c), the FET 11U is turned OFF, and the FET12U is turned ON. Also in this state, the power supply to the windings5Ua, 5Ub from the battery 16 is stopped, and electromotive forces aregenerated in the windings 5Ua, 5Ub. In this mode, the current flows in aroute through the diode 13U, the winding set 5U and the FET 12U by theelectromotive forces. That is, both ends of the winding set 5U aregrounded, and the current refluxes through the aforementioned routeduring the reflux mode.

In the case of FIG. 6( d), the FET 11U is turned ON, and the FET 12U isturned OFF. At this time, both ends of the windings 5Ua, 5Ub areconnected to the battery 16 to be the same potential, and anelectromotive force is generated in the windings 5Ua, 5Ub. The currentflows in the route through the FET 11U, the winding set 5U, and thediode 14U, and the current refluxes the route during the reflux mode.

In the controlling method of the generator according to the presentinvention, the above-mentioned three types of modes are performed asdescribed below. FIG. 7 is an explanatory view showing execution timingof each mode in the U-phase in the controlling method of the embodiment2 of the present invention. Any of the abscissa axes of FIG. 7 show arotary angle of the rotor 3. FIG. 7( a) shows the relationship betweenthe rotary angle of the rotor and the inductance L, FIG. 7( b) shows theenergizing state of the HI side and the LO side in the drive circuit,FIG. 7( c) shows the relationship between the rotary angle of the rotorand the winding voltage, and FIG. 7( d) shows the relationship betweenthe rotary angle of the rotor and the winding current. Here, the U-phasewill be described as an example. However, similar control is performedfor the V-phase and the W-phase.

As shown in FIG. 7, in this embodiment, when the inductance L becomesthe maximum value Lmax (change rate (dL/dθ) of the inductance L is “0”),the power supply is started to the winding 5. The power supply to thewinding 5 is PWM controlled by the gate driver 15U. That is, the supplycurrent rate to the winding 5 is controlled by the continuation time andthe duty ratio under the ON/OFF control of the FET 11U or the like, anda first alternating mode C₁ for alternatively repeating the supply modeand the reflux mode is performed.

In the first alternating mode C₁, the FET 11U of the HI side iscontrolled by a predetermined duty ratio, and the FET 12U of the LO sideis always set to the ON state. When the FET 11U of the HI side is ON, itbecomes the state shown in FIG. 6( a), and the supply mode is performed.On the contrary, when the FET 11U of the HI side is OFF, it becomes thestate shown in FIG. 6( c), and the reflux mode is executed. Thecontinuation time Td of the first alternating mode C₁ is set in responseto the rotational speed of the rotor calculated from the signal of theshaft position sensor 17. At this time, Td can be set by the rotaryangle of the rotor, or may be set to a predetermined angle irrespectiveof the rotational speed or to an angle in response to the rotationalspeed.

During the first alternating mode C₁, the winding current increases atthe supply mode execution time (portion P in FIG. 7( d)), while thewinding current decreases at the reflux mode execution time (portion Qin FIG. 7( d)). In the first alternating mode C₁, the reduction part ofthe winding current in the reflux mode Q is smaller than the increasepart of the winding current in the supply mode P, and the PWM duty ratiois set so that the current waveform generally increases in thesawtooth-like waveform during the time Td. After the time Td is elapsed,the CPU 18 switches the operation mode to a second alternating mode C₂.In the second alternating mode C₂, the reflux mode Q and theregenerative mode (portion R in FIG. 7( d)) are alternately repeated.

The rising trend of the current rate of the reflux mode Q (particularlyQe) in the second alternating mode C₂ is determined depending upon thecurrent value and the rotational speed of the rotor at the reflux modestarting time, and if they are not sufficiently large, the current valuedoes not increase at the reflux mode time. When the current increase atthe reflux mode time is not sufficient, the amount of the regenerativeenergy in the regenerative mode cannot be ensured, therefore the powergenerating efficiency is lowered. On the contrary, when the windingcurrent is controlled so as to increase the current value at the refluxmode starting time, the brake force increases. Therefore, in thecontrolling method of the present embodiment, an average current valuein a region for generating a brake force by the winding current issuppressed by the first alternating mode C₁, and the current value atthe reflux mode starting time in the second alternating mode C₂ can becontrolled to become as large as possible while suppressing such a brakeforce.

In the second alternating mode C₂, with use of the PWM control, the FET11U of the HI side is turned ON/OFF even after the first alternatingmode C₁, and the reflux mode after executing the first alternating modeC₁ is chopped. Here, in the controlling method of the embodiment 1 asshown in FIG. 5, only the reflux mode is performed after the firstalternating mode C₁ is executed, to increase the winding current, thenthe regenerative mode is performed to increase the amount of theregenerative current. However, as described above, there is the case inwhich the winding current increases excessively by the reflux mode afterthe first alternating mode C₁ is carried out, and hence there is aproblem that the load on the power device increases.

On the contrary, in the controlling method of the embodiment 2, thereflux mode and the regenerative mode are not merely executed after thefirst alternating mode C₁ is performed, but the reflux mode and theregenerative mode are repeatedly executed, and the increase in thewinding current in the reflux mode is suppressed suitably in theregenerative mode. Thus, as compared with the case in which the windingcurrent is simply increased in the reflux mode as shown in FIG. 5, asapparent from FIG. 7, in the controlling method for performing thesecond alternating mode C₂, the maximum current value imax can besuppressed to a low value.

At the final stage of the second alternating mode C₂, only theregenerative mode is performed. At the regenerative mode execution time,the winding voltage becomes −E, and in the final regenerative mode Re,the winding current value i is gradually reduced to become “0” shortly.Thus, energy of an amount shown by an area of a portion R of FIG. 7( d)is regenerated to the battery 16. Here, the amount of the regenerativeenergy in the final regenerative mode Re depends upon the current amountat the regenerative mode Re starting time. Therefore, normally, when themaximum current value imax is suppressed, the amount of the regenerativecurrent in the regenerative mode Re is also reduced. That is, in theregenerative mode Re of FIG. 7, a large area (amount of the regenerativeenergy) as in the regenerative mode R of FIG. 5, cannot be secured.

However, in the controlling method of the present embodiment, the refluxmode is executed in the second alternating mode C₂, and the windingcurrent is increased therein. Further, the regenerative mode R isprovided before the regenerative mode Re. Thus, as compared with thecase in which the regenerative mode is merely executed after the firstalternating mode C₁, the amount of the regenerative current is increasedfor the current increased part due to the reflux mode, and theregenerative current is obtained even in the regenerative mode on theway. Therefore, since the amount of the regenerative energy in theregenerative mode Re is lower than the case shown in FIG. 5, the entireamount of the regenerative energy is sufficiently ensured.

Incidentally, since the amount of the regenerative energy is decidedaccording to the amount of current at the regenerative mode startingtime, the amount of the regenerative energy changes according to theduty ratio of the PWM control, the power source voltage, thecontinuation time Td of the first alternating mode C₁, the number oftimes of alternating after the first alternating mode C₁, etc.Therefore, the CPU 18 controls the amount of the regenerative energy bysuitably regulating these values. Further, the CPU 18 always monitorsthe voltage of the battery 16, and performs a PI control by a voltagefeedback, thereby preventing the battery 16 from being overcharged. Inthis case, the PWM duty ratio and the continuation time in thealternating mode may be suitably controlled while observing the batteryvoltage so as to set the battery voltage at a predetermined value. Inthe PWM control, stability of the voltage value is important to ensurethe control accuracy, and the detection of the battery voltage is alsoimportant in this point.

Thus, according to the controlling method of the embodiment 2 of thepresent invention, the amount of the regenerative current can be ensuredto achieve the maximum limit while suitably suppressing the maximumcurrent value imax, and the power generation in a well-balanced mannerbetween them can be performed. Accordingly, a load on the power deviceis reduced, an element having a large capacity is not required, and thecost can be reduced. Further, the amount of the winding current can besuppressed without adding a current sensor, a high speed comparator orthe like, and an increase in cost due to the increase in the number ofcomponents can be prevented.

Embodiment 3

Then, as the embodiment 3, the case in which starting timing of thefirst alternating mode C₁ is advanced from a position where theinductance L becomes the maximum value Lmax, will be described. When thecontrol as shown in FIG. 5 is performed, a measure that the executingtime Td of the alternating mode is increased, times of a reflux mode anda regenerative mode are relatively reduced, and the maximum currentvalue imax is suppressed, is considered. However, when such a measure isadopted, as the times of the reflux mode and the regenerative modedecrease, there is a possibility that a sufficient amount of powergeneration cannot be obtained.

Then, starting timing of the alternating mode is advanced to increase anamount of current to a certain degree at the reflux mode starting timeafter the alternating mode. That is, a control state of advancing anangle may be considered. Particularly, since the winding current becomesan inductance load, even if the first alternating mode is started, thewinding current might not rise in an ideal shape as shown in FIG. 7 inmany cases. On the other hand, when the first alternating mode C₁ isstarted before the Lmax time point by means of the lead angle, theamount of the winding current can be effectively increased at the Lmaxtime point, and the power generating efficiency is improved.

The controlling method of the present invention is effective even whensuch a lead angle is performed. FIG. 8 is an explanatory view showingexecution timing of each mode when the lead angle control is performed,and shows the control state when the above-mentioned lead angle isperformed. In FIG. 8, any of the abscissa axes show a rotary angle of arotor 3 similarly to FIG. 7. FIG. 8( a) shows the relationship betweenthe rotary angle of the rotor and the inductance L, FIG. 8( b) shows theenergizing states of the HI side and the LO side in the drive circuit,FIG. 8( c) shows the relationship between the rotary angle of the rotorand the winding voltage, and FIG. 8( d) shows the relationship betweenthe rotary angle of the rotor and the winding current. Here, the U-phasewill be described as an example. However, similar control is performedfor the V-phase and the W-phase.

As shown in FIG. 8, in this embodiment, before the inductance L becomesthe maximum value Lmax, the power supply to the winding 5 is started. Inthis case, at an FET 11U of the HI side, the power supply is started ata point in time of advancing a time Tah from the time point of Lmax, andat an FET 12U of the LO side, the power supply is started at a point intime of advancing a time Tal from the time point of Lmax. The respectivelead angle times Tah, Tal are set corresponding to the amount of thewinding current at the time of starting the second alternating mode C₂,that is, ON duty ratio of the FET 11U of the HI side. That is, when theON time is lengthened, the value of the current rise in the firstalternating mode C₁ is increased, but even when the amount of thewinding current at the second alternating mode C₂ starting time becomesinsufficient, the lead angle control is performed to lengthen thecontinuation time Td of the first alternating mode C₁. In thisembodiment, Tal>Tah is set, but the Tal and the Tah may be the same time(Tal=Tah).

The first alternating mode C₁ is started from a point in time (time Tahlead angle position) when the FET 11U of the HI side is turned ON. Thefirst alternating mode C₁ is executed under the PWM control by the gatedriver 15U, similarly to the embodiment 2, and a supply mode P and areflux mode Q are alternately repeated. After the time Td is elapsed,the CPU 18 switches the operation mode to a second alternating mode C₂.In the second alternating mode C₂, similarly to the embodiment 1, thereflux mode Q and the regenerative mode R are alternately repeated tothereby suppress the maximum current value imax.

In the controlling method of this embodiment, since the continuationtime Td of the first alternating mode C₁ is lengthened by means of thelead angle, the amount of current at the second alternating mode C₂starting time is increased. Thus, as shown in FIG. 7, it is effectivewhen the first alternating mode C₁ is started from the Lmax time point,and the amount of the power generation becomes in short supply. As thesame time, in the second alternating mode C₂, since the increase in theamount of current is suppressed, the excess increase in the amount ofthe winding current in the reflux mode can be suppressed.

According to the controlling method of the embodiment 3, by combiningthe increase in the amount of current by means of the lead angle and thesuppression of the amount of current in the second alternating mode C₂in a well-balanced manner, the preferable control state capable ofsufficiently securing the amount of the regenerative current can berealized while suppressing the maximum current value imax. Therefore,the amount of the power generation can be increased while the increasein the load on the power device is suppressed to the minimum limit, anda cost rise due to the use of a large capacity element can be prevented.Further, the amount of the winding current can be suppressed withoutadding a current sensor, a high-speed comparator or the like, and anefficient power generation can be performed without increasing the cost.

The present invention is not limited to the above-described embodiments,and various changes and modifications may be made without departing fromthe spirit and scope of the present invention.

For example, in the above-described embodiment, at the time point thatthe inductance L becomes the maximum value Lmax, the alternating mode isstarted. However, the alternating mode can be started from not exactlythe Lmax time point but its vicinity. When the rotor 3 rotates at a highspeed, it is difficult to secure a current value at the reflux modestarting time. Therefore, a lead angle control for starting thealternating mode before the maximum value Lmax position may be performedto increase the current value. Accordingly, the alternating modecontinuation time can be secured longer, and the current value at thereflux mode starting time can be raised, and it is particularlyeffective when the voltage generation is low.

In the above-described embodiment, the battery voltage is monitored bythe CPU 18. However, a current amount detector may be provided in thecontrol circuit, and the current amount is monitored to set the dutyratio of the PWM control, the alternating mode continuation time Td, thereflux mode execution time after the alternating mode, and so on. Note,however, that the voltage detection is generally easy as compared withthe current amount detection, and the voltage detection is advantageousin cost.

Furthermore, in the embodiments 2 and 3, the case that the duty ratio ofthe FET 11U of the HI side is set similarly in the first alternatingmode C₁ and the second alternating mode C₂, has been described. However,the duty ratios in the modes C₁ and C₂ may be set to different values.In addition, the embodiments 2 and 3 are described for the case in whichthe FET of the HI side is used for the PWM drive, and the FET of the LOside is used for a phase control. However, the FET of the LO side may beused for the PWM drive and the FET of the HI side may be used for thephase control.

On the one hand, the generator according to the present invention may beused as a power generation facility of a wind power generator. In thewind power generator, rotary blades are operated by wind power toconduct power generation, and a large wind power is required at thestarting time of the rotary blade. A generator cannot be started if thewind does not have a wind speed of a certain degree. Therefore, in thecase of a slight breeze that does not satisfy a wind speed capable ofstarting the rotary blade, there is a problem that power generationcannot be performed even if the wind blows.

In that case, this generator can be used as an SR motor. It is possibleto use the generator as a motor to start the rotary blade, and after therotary blade is once started, to use the generator as a generator.Therefore, even in the case of the above-mentioned slight breeze, therotary blade can be started by the motor, and thereafter the rotaryblade can be rotated by the wind power. In this case, the using time ofthe generator as the motor is short, and acquisition energy by the powergeneration thereafter is much larger. Thus, the wind power generator canbe operated from the slight breeze state, and the power generatingefficiency can be improved.

1. A method of controlling a generator including a stator having aplurality of salient poles, a rotor having a plurality of salient poles,and a winding wound around the stator, a quantity of the salient polesof the rotor being different than a quantity of the salient poles of thestator, said method comprising: executing an alternating mode byalternately repeating a supply mode for supplying power from a powersource to the winding and a reflux mode for setting both ends of thewinding to the same potential; and after said executing of thealternating mode, further executing the reflux mode, and thereafterexecuting a regenerative mode for recovering in the power source anelectromotive force generated in the winding; wherein the generator iscontrolled by a switching circuit having a switching element and a diodeconnected to both ends of the winding, and the switching element is PWMcontrolled to execute the alternating mode.
 2. The method of claim 1,further comprising detecting a voltage of the power source, wherein saidexecuting the alternating mode includes controlling a continuation timeof at least one of the supply mode and the reflux mode based on thedetected voltage.
 3. The method of claim 1, further comprising detectinga voltage of the power source, wherein said executing the alternatingmode and said further executing the reflux mode includes controlling acontinuation time of at least one of the alternating mode and the refluxmode based on the detected voltage.
 4. The method of claim 1, whereinthe supply mode is started at a point in time when an inductance of thewinding achieves substantially a maximum value.
 5. A method ofcontrolling a generator including a stator having a plurality of salientpoles, a rotor having a plurality of salient poles, and a winding woundaround the stator, a quantity of the salient poles of the rotor beingdifferent than a quantity of the salient poles of the stator, saidmethod comprising: executing a reflux mode in which both ends of thewinding are set to the same potential after executing a supply mode forsupplying power from a power source to the winding; and after saidexecuting of the reflux mode, executing a regenerative mode forrecovering in the power source an electromotive force generated in thewinding; wherein the generator is controlled by a switching circuithaving a switching element and a diode connected to both ends of thewinding, and the switching element is PWM controlled to execute thealternating mode.
 6. The method of claim 5, further comprising detectinga voltage of the power source, wherein a continuation time of at leastone of the supply mode and the reflux mode is controlled based on thedetected voltage.
 7. The method of claim 6, wherein the supply mode isstarted at a point in time when an inductance of the winding achievessubstantially a maximum value.
 8. The method of claim 5, wherein thesupply mode is started at a point in time when an inductance of thewinding achieves substantially a maximum value.
 9. A method ofcontrolling a generator including a stator having a plurality of salientpoles, a rotor having a plurality of salient poles, and a winding woundaround the stator, a quantity of the salient poles of the rotor beingdifferent than a quantity of the salient poles of the stator, saidmethod comprising: executing a reflux mode in which both ends of thewinding are set to the same potential after executing a supply mode forsupplying power from a power source to the winding; after said executingof the reflux mode, executing a regenerative mode for recovering in thepower source an electromotive force generated in the winding; anddetecting a voltage of the power source, wherein a continuation time ofat least one of the supply mode and the reflux mode is controlled basedon the detected voltage.
 10. The method of claim 9, wherein the supplymode is started at a point in time when an inductance of the windingachieves substantially a maximum value.